<script>
    //数组实现了Symbol(Symbol.iterator): ƒ values()函数（接口）
    let users=["mark","jack","rose"];
    for(let user of users){
        console.log(user);
    }
    console.log(users);
    //调用数组中的Symbol.iterator函数，获得一个含有next方法的对象
    let iterator=users[Symbol.iterator]();
    //调用next方法
    console.log(iterator.next());  //{value: 'mark', done: false}
    console.log(iterator.next());  //{value: 'jack', done: false}
    console.log(iterator.next());  //{value: 'rose', done: false}
    console.log(iterator.next());  //{value: undefined, done: true}
</script>